Impedance Basics
The basic specification of almost all headphones is impedance. In fact, most audio sources such as a DAP, phones or amplifiers also relies heavily on the concept of impedance. Even though most have seen the term on headphones and other devices, it is not well understood as an important headphone purchasing criteria. Today we demystify the topic of impedance (not spelled impedence) and how you can begin using it to improve your audio experiences.
What is Impedance
Impedance is simply the measure of resistance to electrical flow. It is measured as ohms. In DC systems, resistance and impedance are equal. It is the difference between the voltage across an element and the current (R = I/V). The symbol Z stands for impedance.
Impedance Essentials
There are many terms you need to know when describing impedance. If the impedance is a simple electronic circuit, it may be called output (or source impedance) while the impedance for the headphones can be called load impedance.
Headphone impedance can be rated from 8 to 600 ohms. However, a standard of 32 ohms is becoming more common in the headphone and earbud industry. The audio source impedance is usually very low. It can be less than 4 ohms in most cases and close to 0 in others. That being said, the audio source can reach 120 ohms for tube amplifiers that are output transformer-less (OTL).
What is Impedance Matching?
Impedance matching refers to the interaction of the source impedance and the headphone’s impedance. The headphones and source must be paired well to ensure high quality audio. The impedance range of the source and headphones do not necessarily match, rather the ranges are complementary to arrive at a perfect match.
It is sufficient to know that the audio source and headphones’ impedances must not be equal. It is important to note, different impedances require different sources. Equal source and load impedance increase the power that can be transferred between headphones and amp, but it reduces frequency bandwidth. This is not what we want for a quality, high fidelity listening experience.
Low impedance headphones (< 50ohms) are specifically designed to work with smart phones and other low voltage mobile devices. On the other hand, high impedance headphones (>50 ohms) require strong amplification in order to work well.
Headphone Impedance: High or Low?
Headphones that have an impedance higher than 100 ohms tend to be older designs or are made for professional studios. In order to make a simple, inexpensive headphone circuit, receivers from the pre-1990s used resistors.
This was so common that, even in 1996, the recommended source output resistance was 120 Ohms. It was also claimed that source impedance had little to no effect on the performance.
Older circuits work best with high-impedance headphones. High impedance headphones can be used to connect multiple pairs of headphones simultaneously for studio applications. The high impedance load, without getting into too much detail, preserves the source voltage so that multiple pairs can be driven.
Modern headphones are made to appeal to as broad a market as possible. They must also work well on mobile devices. Due to the widespread popularity of the iPhones, Androids, and various battery-powered music players, headphones with lower impedance (around 32 ohms) have become the industry sweet-spot.
Do Headphones with Multiple Impedances Exist?
Most headphones you will find online or in a retail store will have only one impedance. Beyerdynamic is one the few major companies that can produce multiple impedance within the same model headphone.
It is possible to get a better sound quality with high-impedance headphones if they are properly matched with an amplifier. This does not mean that low-impedance headphones with excellent sound quality are impossible to find.
What is Headphone Sensitivity?
Sensitivity is the measurement of volume in a headphone at a particular power rating. The frequency at which headphones are sensitive is 1 kHz at 1 mW power. The range of sensitivity ratings is typically between 90-105dB, with outliers being extremely sensitive or insensitive.
With listening volumes of 60-80 decibels, it would seem that a maximum of 1 mW should be sufficient to produce adequate volume. Sensitivity ratings are not enough. It is also important to consider music dynamics and total harmonic distortion (THD) of the amp.
The recommended dynamic range, which is the maximum to lowest level of sound reproduction for highly dynamic classical music, is 20 db. To put this into perspective, a 20 db increase in volume requires that the headphones be rated at 100 times their original power.
This dynamic range means that a 1MW nominal sensitivity rating can quickly turn into a 100MW power requirement for an amp. Although this is not universal, amplifiers are more likely to produce distortion with increasing power. An amplifier rated at 100 mW with low distortion might be required in this case. Amplifier power specifications are usually given at 1% THD.
Do Sensitivity and Impedance affect Volume?
Although they are closely related, impedance and sensitivity do not necessarily go hand in hand. When pairing headphones with sources, both must be taken into consideration to strike the proper sound balance.
Although it is tempting to simply describe impedance by using Ohm’s Law (Voltage = current * Resistance), Ohm’s Law really only applies to DC (direct current). If impedance were the same thing as resistance, headphones with identical impedances would be quieter than those with lower impedance given the same source of voltage.
Similarly, understanding impedance is not as easy as understanding load resistance. It is also important to consider the source output impedance. The load on the transistors or tubes and the current (or bias) are also important. Because the output impedance of amplifiers is not zero, they will deliver more voltage to higher impedance loads.
High impedance loads that have a high output impedance can produce more volume. If the current is limited, an amplifier might not be able to produce enough power to a low-impedance load. However, it could be able to make plenty of power to a high-impedance load. Each amplifier design will have its own specifications and capabilities.
Headphone Sensitivity and Impedance Comparison
Further complicating matters is the lack of consistency in headphone design when it comes to impedance or sensitivity. Low impedance headphones can be very inefficient, and vice versa. A headphone driver can reproduce a wide variety of frequencies, which is obvious. The perfect driver would be consistent over the entire audible frequency range.
Resonant Frequency for Dynamic Driver Headphones
The voice coil on a pair of dynamic headphones is designed to control the driver and ensure good behavior at its resonance frequency. Keep in mind that most manufacturers list impedance at 1Khz on the specifications of headphones.
Published impedance will likely be significantly lower than the driver’s resonant frequency. The frequency impedance graph of the driver shows a more precise picture. The resonant frequency can cause this resistance to multiply many times.
The impedance response of dynamic driver headphones is not uniform across all frequencies. Some designs are flatter than others.
Load Impedance and Source
An amplifier’s distortion performance is affected by the load impedance of headphones. The designer optimizes the operating voltage and current (or bias), for tubes or transistors in amplifiers for low or high impedance loads or a combination of both.
When the amplifier is optimized to high impedance, connecting a low-impedance load will reduce power and increase distortion. Many amplifiers are equipped with multiple outputs and switches, which allow them to adapt to different impedance loads while remaining optimally biased.
At impedance spikes the ratio of output impedance to load impedance changes dramatically. This can lead to driver damage and audible distortion which is an unpleasant listening experience overall.
For portable power requirements, equal impedance between headphones and source is ideal yet will not guarantee sound quality.
How to Get the Best Performance from Headphones
Headphone and source impedance mismatches are key to providing optimal sound quality. Headphone and source matching is often known as pairing, synergy, or just matching but it’s actually complementing more so than matching. Since impedance can affect volume and sound quality, your next pair of headphones must have the correct amp voltage.
High Source Impedance + Low Headphone Impedance
Combining high output impedance with low headphone impedance can lead to serious problems. This is a common scenario for OTL tube amplifiers, which can create higher harmonic distortion, lower dampening, bass roll-off, and noise.
Headphone Distortion, Dampening, & Roll-Off
The typical solid-state headphone amplifiers have a very low output impedance and can be matched with various headphones. Pairing a headphone with a load impedance lower than the amplifier’s source will cause audible distortion. However, low impedance headphones should not be used with high output amplifiers but very high impedance headphones (>200ohms) for optimal sound clarity.
The driver’s control over an amplifier’s damping factor is essentially the amplifier’s ability to control the driver’s movement after the signal has ended. Low frequency reproduction is where damping factor is most evident. Low damping can result in loose, boomy, and unclear bass. High damping, however, tends to make the bass sound tighter, cleaner, and less warm.
The headphone damping factor can be defined as the ratio of the driver impedance to the amplifier impedance. The first number in the ratio is the driver impedance and the second the source output impedance. You can generally divide the headphone’s impedance by 8 to get the maximum source output. (32 ohm headphones/8 = 4 ohm maximum output impedance).
Bass roll-off is a frequency response playback that audibly decreases towards lower frequencies. Low-frequency response in headphones and amplifiers matching is complicated as several factors contribute to bass roll-off. Specifically, the factors that combine to effect roll-off include resonance frequency, inductive reactance, transformers, and capacitors involved. Low damping factors can lead to a perception of a roll-off below the resonant frequency or that the amp and headphones are poorly matched.
What is Headphone Impedance?
Impedance is a technical measurement. Without equations and scientific jargon, it is difficult to understand. It will be simplified and broken down into headphones with high impedance and low impedance.
Low impedance headphones (<50ohms) are able to produce high levels of audio with little power. Low impedance headphones, for example, will work well when used with devices with weak amplifiers, such as phones and portable music players.
Higher impedance headphones (>50 ohms) require greater power to produce high levels of audio. They are therefore protected against damage from overloading. They can be used with a greater range of audio equipment. As an example, DJ headphones is generally range between 25 and 70 ohms.
Low impedance headphones are more vulnerable to “blowouts” when they’re connected to more powerful amplifiers. You can connect a pair of lower-priced earbuds with low impedance (18 ohms) and a DJ mixer to blow them out.
You should research the equipment that you will be using with the headphones if they are very high in impedance.
What Does Ohm & Impedance Mean Headphones?
Impedance is a basic specification in all headphones and in every audio source. The resistance of headphones and earphones to electric currents transmitted by amplifiers is called impedance.
The impedance can be measured in ohms and is the relationship between voltage and current. It can vary from 8 to 600 ohms depending on the brand of the headphones or earphones. For audio aficionados, an impedance of between 20-40 ohms would typically be a very safe choice.
Drilling in deeper, the design of the voice coils determines the impedance of the headphones. The length and size of the wire plus magnet strength and number of coils directly affects impedance and sound clarity.
Higher Impedance Headphones
Higher Impedance is commonly referred to as 25V 70V 100V. High-impedance headphones are best suited for studio applications and not casual listeners. These headphones require more power to achieve a solid listening level. The headphones with higher impedance (25 ohms and over) usually require more voltage.
Higher-impedance coils have more winding. This can lead to a better motor system and a lower number of compromises.
Headphones with Lower Impedance
Higher-impedance headphones have thinner wires and windings. Low impedance headphones (less than 25ohms) will require less power to produce high levels of audio. These headphones are intended for portable phones and portable music devices.
The headphones with lower impedance can be used to achieve a higher volume and less drain on your smartphone’s battery than headphones with higher Impedance. This type of headphone is not typically compatible with powerful amplifiers due to their low threshold limit. Otherwise, you will have to deal with the blowout.
What does impedance mean in simple terms?
Impedance (denoted with a letter Z) is the opposition an electronic component, circuit or system presents to an alternating and/or directed electric current. Impedance can be described as a vector (two-dimensional), quantity that consists of two independent scalar phenomena (one-dimensional), resistance and reactance.
What is resistance and impedance?
In an electrical diagram, resistance is used to regulate the flow of current. This current can be AC or DC. The current flow is determined by resistance, regardless of the current type. Impedance can be described as a combination of capacitive, resistive, or inductive reactance.
What is the purpose of impedance?
Because it allows the simple linear law to relate sinusoidal voltages with currents, the notion of impedance can be useful in AC analysis of electrical network.
What is the difference between impedance and voltage?
The impedance (Z) in a circuit’s circuit is equal to V (volts), the maximum potential difference or voltage across the circuit divided by I (amperes through the circuit). Or simply Z = V/I. Simply put, the ohm is the unit of impedance.
What are impedance give an example?
An impedance can be defined as any obstacle or measure that blocks an electric current from flowing energy when voltage is applied. A mismatch in volage and current in your headphones when attempting to be paired with an amplifier.
What’s another word for impedance?
Definitions of impedance: a material’s resistance to electric current flow; measured in Ohms. Other words that are synonymous with impedance include electric resistance, electrical resistance, ohmic resistance, resistance, and resistivity.
What is inductance and impedance?
With frequency and inductance, the inductive reactance rises. Capacitive reactance decreases as a function of frequency and capacitance. Impedance is total resistance to reactance and resistance.
What is difference between capacitance and impedance?
Capacitance can be defined as the amount of charge stored/displaced on a capacitor divided the potential difference across it. It can also be calculated using the size of plates and primitivity of insulator.
Can impedance be less than resistance?
Resistance refers to DC (direct currents), whereas impedance refers to the AC equivalent. Reactance can also be called impedance, which is a general term that refers to resistance.
Also, resistance can be defined as the opposition to an electric current. Pure resistance doesn’t change with frequency. Typically, the only instance of resistance that is being considered is DC (direct current — non-changing) electricity.
Resistance can be caused by electrons colliding with the conductor’s ionic lattice, which means that electrical energy is converted to heat. Different materials have different resistivities, which are properties that determine how resistive a material will be for a given dimension.
What Causes High-Impedance?
There are many factors that can cause increased resistance, such as corrosion, loose connections and damaged conductors.
What Happens with High-Impedance?
High impedance loads that have a high output impedance can produce more volume. If the amplifier is not current limited, it may not be able to produce much power into low impedance loads. However, it can make plenty of power into high impedance loads.
What Does High-Impedance Mean?
High impedance in electronics means that a point within a circuit permits a small amount of current through per unit of applied voltage. Low impedance circuits allow for low current and high voltage.
Do DC Circuits have Impedance?
Reactance is very low in pure DC systems, so it is common to ignore the reactance component of impedance when doing DC analysis. This would mean that resistance = Impedance. You can actually do all DC network analysis with Impedance, instead of just ignoring it.
Is Impedance the Same as Ohms?
The letter Z is used to represent the “impedance” in circuits and is measured in Ohms. Because all three forms of resistance are opposition to current flow, the term “impedance” can also be used to describe capacitive reactance or inductive reactance.
What is Difference Between Resistor and Impedance?
It is important that you understand that reactance refers to the resistance provided to AC current by capacitors and inductors, while impedance refers to the sum of reactance and resistance.
Do High-Impedance Headphones Sound Better?
The 250- and 600-ohm headphones have a lower moving mass than 32-ohm models. This is why high-impedance headphones are better.
What is Good Impedance in Headphones?
The impedance can be measured in ohms. It can vary from 8 to 600 ohms depending on the brand of the headphones/earphones. For audiophilia, however, an impedance of between 20-40 ohms would be a good choice.
Is 32-ohm Impedance Good for Earphones?
32ohm or below is the impedance most commonly found on commercial headphones and earphones. These headphones are best suited to consumer devices with built-in amplifiers because of their low ohmage.
Does Impedance Affect Sound Quality?
To ensure sufficient volume and sound quality, the headphone and source are matched with their impedance. Match refers to ‘complementary’, not ‘equal’. A headphone should be paired with an impedance 2.5-8 times greater than the source impedance to achieve good results.
Conclusion: Impedance
If you recall, there are two types of impedance: source impedance or headphone impedance. To ensure sufficient volume and sound quality, impedance matching between source and headphone is done. Match refers to ‘complementary’ and not ‘equal’.
A headphone should be paired with an impedance 2.5-8 times greater than the source impedance to achieve good results. This is known as the “rule of eights” and helps to maintain driver control (damping). A headphone that has a lower or equal impedance to the source will result in poor sound quality and unpredictable results.
Sensitive headphones (100 dB+), with low impedance (8-832 ohm), will usually pair well with a portable source (such a phone), without the need for an amplifier. A more robust amplifier will provide better sound quality and volume than a portable device (or phone) that is less sensitive (less than 95dB) or medium to high impedance headphones (more than 50ohm).
FAQ: Headphone Impedance
Why is impedance so important in circuits?
If not properly managed, impedance can have a significant negative effect on circuit performance. Reflections can occur along the path from source to load if there is not proper impedance matching.
What’s the purpose of impedance in electronics technology?
Capacitors use impedance to control the flow of electricity on a circuit board. Your electronics that use alternating currents can get fried without the control and adaptability of capacitors.
What’s the point of high impedance?
High impedance in electronics means that a node allows only a small amount of current to pass per unit of applied voltage.
What happens when impedance isn’t matched?
Maximum power won’t be delivered if the impedances don’t match. Standing waves can also form along the line distorting the sound waves as the load won’t absorb all the power that’s sent down the line.
Which is better, low or high impedance?
Higher impedance equipment is more effective because it produces better sound quality. Low impedance equipment is better for casual listening on smartphones or laptops.